1. Field of the Invention
The present invention relates to a throttle body for a fuel injection device for an internal combustion engine.
More specifically, the invention relates to a throttle body of the type comprising:
a housing in which an air inlet duct is formed, and
a butterfly in the form of a substantially circular or slightly elliptical disk mounted on a central rotation spindle transversal to the duct, splitting this duct into an upstream part and a downstream part and movable between a minimally open position and a wide open position for which the plane of the butterfly is oriented substantially parallel to the axis of the inlet duct, the part of the butterfly which rotates toward the upstream part of the duct and the part which rotates toward the downstream part, from the minimally open position, being known respectively as the upper wing and the lower wing and having the shape of a flat half-disk having an edge face of small thickness with respect to its area, the upper wing thus having an upstream face and a downstream face, the duct being intended to have passing through it a stream of gas the velocity of which is at a maximum as it passes a portion of the upper wing of the butterfly.
2. Background Art
The gas deflected by the butterfly has a velocity gradient which reaches a maximum over a certain portion of the upper wing of the butterfly. This may give rise to a whistling effect at certain angles of opening of the butterfly when the stream of gas is deflected sharply downstream of the butterfly, for example by a wall of the inlet manifold positioned in close proximity to the outlet of the housing, this being true irrespective of the known shapes of butterfly.
The object of the present invention is to provide a throttle body in which this kind of whistling is eliminated irrespective of the angle of opening of the butterfly.
To this end, according to the invention, a throttle body of the type in question is essentially characterized in that a recessed relief is formed in the downstream face of the portion of the upper wing of the butterfly which experiences the maximum gas velocity, the recessed relief opening radially into the peripheral lateral face of the butterfly and being delimited by surfaces of which the intersections with the downstream face are sharp edges.
By virtue of these provisions, the recessed relief dissipates some of the energy of the stream of gas which flows over the butterfly so that the energy available for producing audible noise is greatly reduced and the whistling is therefore eliminated, whatever the angle of opening of this butterfly.
In preferred embodiments of the present invention, recourse is further had to one and/or more of the following arrangements:
the recessed relief is delimited by an upper face from which there extend, as far as the downstream face, two substantially radial faces substantially facing each other, and a transverse face connecting the substantially radial faces together and which are such that the intersections of the substantially radial faces and the transverse face with the downstream face are sharp edges,
the upper face, the substantially radial faces and the transverse face are substantially flat.
the intersections of the transverse face with the substantially radial faces and the upper face are sharp edges,
the substantially radial faces are connected to the upper face with a rounded shape,
the substantially radial faces diverge from one another from the transverse face and toward the peripheral lateral face of the butterfly,
the upper face of the recessed relief is substantially parallel to the downstream face and the upstream face, of which the intersections with the peripheral lateral face of the butterfly are sharp edges,
at the recessed relief, the remaining thickness of the butterfly is less than about 1.5 mm, the width of the recessed relief, considered in a substantially circumferential direction, is substantially between 10% and 25% of the diameter of the butterfly, and the length of the recessed relief, considered in a substantially radial direction, is greater than about 50% of the width of said relief, and
the length of the recessed relief is less than about 90% of the width of said relief.